[Nml-wg] DCN glossary

[John Vollbrecht]

I think Evangelos is right -- we are talking about slightly different  
things.

I think there are several differences  that might be considered

1) for me the difference between a "path" and a "strict path"
	I think that what Freek describes is a strict path in my  
terminology.  It contains edgepoints (i.e. links), and contains all  
the (relevant) links
	A path is just a way to get between two edge points.  It may be  
described in a number of ways
		a) just the two endpoints
		b) endpoints + some intermediate hops - where hops can be links or  
other topological element (i.e. domain, node, port)
	note that for me a path does not have to specifically define every  
link in the topology between end points - it is "potential"

2) Freek seems to assume that adaptations occur only at links. In my  
model the hops in a path may be domains, for example.  The  
implication is that domains must be able to do adaptations.

3) My potential paths may assume adaptations are possible without  
knowing  for sure that they are.  I think the potential path probably  
needs a name different than the actual path

4) I have taken to using circuit as a path with specific resources  
assigned to it.  It is possible, for example, to have multiple  
circuits using the same path.  Circuits are what DCN creates over  
paths.  Adaptations take place on circuits in my view, not paths.  It  
seems to me paths have adaptation points in them but don't do the  
adaptation (perhaps this is not right - perhaps adaptations are part  
of paths and circuits -- ?)

John

On Jul 1, 2008, at 5:24 PM, Evangelos Chaniotakis wrote:

> Hi,
>
> My opinion is that we're talking about slightly different things.
>
> Path in the sense Freek defines it seems to represent a "finalized"  
> object while the way John describes it is closer to an "unfinished"  
> object that we would find in a service request.
>
> I think both approaches have value, and are in fact very close but  
> maybe we would like to  to differentiate between them?
>
>
> On Jul 1, 2008, at 8:44 AM, John Vollbrecht wrote:
>
>>
>> On Jul 1, 2008, at 9:09 AM, Freek Dijkstra wrote:
>>
>>> John Vollbrecht wrote:
>>>> Attached is a DCN glossary which is part of DCN architecture and
>>>> DCN reservation documents.
>>>
>>> Thanks John!
>>>
>>>> path - a connection between a source and destination.  A path is a
>>>> sequence of hops.
>>>
>>> I would argue that a path is a sequence of edges/links rather than
>>> hops. That way I can distinguish between two links between the same
>>> hops, and can more easily between different types of relations
>>> between hops (link, cross connect, adaptation, de-adaptation)
>>>
>>
>> I  think of a path a a sequence of hops because a requested path may
>> contain some but not all intermediate hops, and hops may be domains
>> rather than links.
>> A strict path is a sequence of links.
>>
>> There may be multiple paths between hops but paths may be "potential"
>> or requested as well as confirmed and strict.

John Vollbrecht, Senior Network Engineer
Internet2
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